Method of concentrating a chromite-containing ore



United States Patent 3,473,656 METHOD 0F (ZONCENTRATING A CHROMITE- CONTAINING ORE Filip Ser, Neznanog Junalra 19, Milan Milosevic, Mestroviceva 15, and Predrag Bulatovic, Stevana Sremca 13, all of Belgrade, Yugoslavia No Drawing. Filed Jan. 22, 1968, Ser. No. 699,353 Claims priority, application Yugoslavia, July 28, 1967, P 1,508/67 Int. Cl. B03d 3/06, 1/00 US. Cl. 2095 6 Claims ABSTRACT OF THE DISCLOSURE A method in which a chromite-containing ore is ground to a fineness in which 70 to 73% is of a size below 0.074 mm. the ground ore then being dispersed with sodium silicate in an alkaline medium whose pH is maintained at 11.5 to form a pulp, after which carboxymethylcellulose is added to the mixture to selectively flocculate the gangue in the ore, the chromite then being separated by flotation as a consequence of the addition to the pulp of an anionic collector.

BRIEF SUMMARY OF THE INVENTION There are present in the world well known reserves of low-grade chromite ores which cannot be economically concentrated by presently known methods of extracting minerals from raw material.

One known method for the concentration of chromite ores, the gravity method of concentration, is uneconomical and technologically complex.

An object of the invention is to provide a method for the concentration of low grade chromite ores which is economical and technically feasible. A feature of the invention is that it enables the utilization of low-grade deposits of chromite ores.

The method of the invention is characterized by the introduction of a flocculant-electrolyte of definite electrical charge into a system of stable dispersion, which flocculates only certain minerals of a definite electrical charge, and at the same time eflects hydrophilization at the surface. Thus, a flocculant of a definite electrical charge selectively flocculates the minerals and at the same time serves to enable its selective separation.

In the method of the invention, it is necessary to grind the ores to a state of granulation such that 70 to 73% of the particles are of a size which is below 0.074 mm. After the grinding, the ore is dispersed with sodium silicate in a basic medium at a pH of 11.5 to form a pulp. The pH is controlled by the addition of sodium hydroxide. Thereafter selective flocculation of the gangue is etfected by the addition of carboxymethylcellulose and flotation of the non-flocculated chromite is efiected by the addition of tall-oil to the pulp as an anionic collector.

The quantity of sodium silicate which is added with the ore is 1500 grams per ton (gr./t.). The carboxymethylcellulose is added in an amount of between 125 and 250 gr./t. and the amount of tall-oil utilized is 500 to 15 00 gr./t.

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The method is distinguished from known methods by the fact that it is not necessary to perform any preliminary slime removal from the ore and that the flotation with an anionic collector is performed in an alkaline medium.

According to the method of the invention, there are obtained concentrates of chromite with 5060% Cr O with 80-85% recovery from the ore. The ore at the beginning of the treatment comprises: 18.1322.08% Cr O 9.5- 11.2% FeO; 23.98% SiO 1.3% CaO; 12.14% A1 0 DETAILED DESCRIPTION The invention will be further described with reference to the following examples:

Example I An ore with a content of 18.13% Cr O 9.5% FeO; 23.98% SiO 1.3% CaO; 12.14% A1 0 and wherein the ratio of Cr:Fe is 1.68 was ground to a fineness such that 73% of the particles were of a size below 0.074 mm. A dispersion is achieved with 1500 gr./t. of sodium silicate to form a pulp at a pH of 11.5. Selective flocculation is then achieved by the addition of 120 gr./t. of carboxymethylcellulose. Flotation is performed by the addition of tall-oil as an anionic collector in a quantity of 500 gr./t.

The obtained concentrate of chromite had the following composition: 52.16% Cr O 16.40% FeO; 3.72% SiO 11.88% A1 0 and the ratio of CrzFe is 2.80.

Thus about 80% of the chromite is recovered, while the tailing contains only 5% Cr O Example II An ore Was used which had the following composition of pertinent substances: 22.08% Cr O and 11.2% FeO. The ore was ground to a fineness in which of the particles were of a size below 0.074 mm. The ground ore was dispersed with 1500 gr./t. of sodium silicate in a basic medium having a pH of 11.5. The pH was controlled with NaOH. Selective flocculation is next performed by the addition of 250 gr./t. of carboxymethylcellulose and flotation is achieved with the addition of tall-oil, as an anionic collector in an amount of 1500 gr./ t.

The obtained concentrate of chromite was 60.11% Cr O while the ratio of CrzFe was 2.76, the chromite recovery being What is claimed is:

1. A method of concentrating a chromite containing ore, said method comprising grinding the chromite containing ore to a fineness where 7073% of the ground ore is of a size below 0.074 mm., dispersing the ground ore with sodium silicate in an alkaline medium which is at a pH of 11.5 to form a pulp; selectively flocculating the gangue in the ore by adding carboxymethylcellulose to the pulp, and effecting flotation of the non-flocculated chromite by adding an anionic collector to said pulp.

2. A method as claimed in claim 1, wherein the chromite containing ore comprises: 18.1322.08% Cr O 9.511.2% FeO; 23.98% SiO 1.3% C210 and 12.14% A1 0 3. A method as claimed in claim 1, wherein the quantity of sodium silicate used for dispersion is 1500 grams per ton.

4. A method as claimed in claim 1, wherein the pH of the medium is controlled by adding thereto, sodium hydroxide.

5. A method as claimed in claim 1, wherein the quantity of carboxyrnethylcellulose used for flocculation is between 120 and 250 grams per ton.

6. A method as claimed in claim 1, wherein the anionic collector is tall-oil which is added in an amount of between 500 and 1500 grams per ton.

References Cited UNITED STATES PATENTS OTHER REFERENCES RI 5576, U.S. Bureau of Mines, 1960 pp. 11-13.

HARRY B. THORNTON, Primary Examiner ROBERT HALPER, Assistant Examiner U.S. Cl. X.R. 

